Pasteurizing device



Patented Feb. 3, 1942 UNITED STATES PATENT OFFICE.

PASTEURIZING DEVICE Newel F. Hodgdon, Cedar Rapids, Iowa Application October 14, 1940, Serial No. 361,032

4 Claims.

This invention relates to devices for use in the pasteurization of fluids, such as milk and cream, and has particular relation to an improved form of heat transfer coil for use in such devices.

Pasteurizing equipment, as it is normally constructed for use in sterilizing milk and cream or the like, comprises a vat for receiving the fluid and a revolvable tubular heat transfer coil through which steam or cooled brine may be directed. In such devices, the vat is filled with the fluid to be sterilized and steam or hot water is forced through the coil while the coil is rotated, by any convenient drive means, to agitate the fluid. This process is continued until the fluid has reached the required temperature for proper sterilization, after which the heat transfer coil may be disconnected from the heat source and connected to a brine cooling system. Cooled brine may be circulated through the coil to chill fluids such as milk or cream.

It has been my experience, with devices of the prior art, that there is usually a considerable temperature difference between the inlet and outlet ends of the heat transfer coil, and I have found this to result in temperature differences as high as degrees in the fluid in the extreme ends of the vat.

This is obviously not a good condition, and it is accordingly one of the primary objects of my invention to improve this condition by providin means for maintaining a more uniform average temperature in the coil throughout the length of the vat. I

Another object of my invention is the provision of an improved heat transfer coil for pasteurizers, and particularly a new arrangement for such a coil whereby the temperature drop between the farthest portions of the coil is at a minimum. a

A further object'of my invention is to provide improved means for mounting such heat transfer coils and for utilizing the central or supporting shaft as a portion of the heat transfer surface.

Other and further features and objects of the invention will be more apparent to those skilled in the art upon a consideration of the accompanying drawing and following specifications, where are disclosed several exemplary embodiments of the invention, with the understanding, however, that such changes may be made therein as fall within the scope of the appended claims, without departing from the spirit of the invention.

In said drawing:

Figur 1 is a view, partly in section and partly in side elevation, of a pasteurizer employing a heat transfer coil constructed in accordance with my invention.

Figure 2 is a view, partly in elevation and partly in section, illustrating, in particular, the relation of the parts of the coil and also the central shaft and the coil attachment and connection means in a heat transfer unit constructed in accordance with a preferred embodiment of my invention. The coils themselves are illustrated more or less schematically, and

Figure 3 is a view similar to Figure 2 but illustrates a coil attachment and connection means constructed in accordance with a modification of my invention.

Referring now to the drawing, and particularly to Figure 1 thereof; the pasteurizer illustrated is constructed more or less in accordance with common practice,,with the exception of the heat transfer coil, and consists in general of a metal lined, insulated vat indicated at Ill, open at the top and provided with a removable cover II, a heat transfer coil indicated generally at I2, and a longitudinally extending tubular shaft I3 through which steam, hot water, or a cooling medium such as cold brine may be fed to the coil I2.

The central shaft I3 is provided with tubular stub shaft portions I4 and I6 which are supported in bearings I! in the end walls of the vat. These bearings include packing glands for preventing loss of fluid from the vat and also for preventing the passage of any lubricant from the bearings into the vat.

The outer ends of the stub shafts I4 and I6 are provided with rotating joints or outlet boxes I8 and I9 having packing glands or stuffing boxes 2| and 22 respectively. These outlet boxes are connected together by means of piping, indicated at 23 and 24, into which piping a steam injector 26 is connected. Steam entering this injector passes through the pipe 23 and into the heat transfer coil I2 and, at the same time, causes a recirculation of steam condensate through the system. All excess condensate is exhausted from the piping system through an overflow pipe 21 connected to the outlet box I9.

In pasteurizing fluids such as milk, the vat is filled with the milk and steam turned through the coil. The entire coil is then rotated, in order to agitate the milk, by any suitable means such as the worm gear 28 affixed to the stub shaft I I, a worm 29, and an electric motor, not shown, for driving the worm.

It is the usual practice with coils constructed in accordance with the prior art, to pass the heating or cooling fluid through the coil from one end of the vat to the opposite end, and it is obvious that the fluid adjacent the ends of the vat will be subject to temperatures depending upon the temperature drop throughout the entire length of the coil. An alternative method of construction has been to arrange the coil in two sections and feed the heating or cooling medium through the two sections simultaneously or in parallel. This construction has at least one major' disadvantage in that one of the parallel portions of the coil may become air-locked, thus making only one-half of the entire coil effective.

It is the purpose of my invention to arrange and mount the heat transfer coil in such a manher that steam or the like passes from one end of the vat to the opposite end but through only one-half of the coil whereby the temperature drop is considerably less than in the usual device of this nature. The steam or its condensate is then returned through the central shaft or pipe back to the inlet end of the remaining half of the coil, through which it then passes and in which it experiences a further drop or rise in temperature as the case may be.

In Figure l the steam or the like enters through the tubular spindle or stub shaft I4, passes through a diverting fitting 3| into the first portion 32 of the coil from which it is discharged into the fitting 33 and diverted back through the tubular central shaft 13 into the second half 34 of the heat transfer tube from which it is discharged through the fitting 33 and through the stub shaft or spindle It.

Figure 2 illustrates the construction of the diversion fittings 3i and 33 and schematically illustrates-the arrangement and relation of the tubing and fittings and the flow of the heating or cooling fluid therethrough.

The diversion fittings 3| and 33 are preferably castings of rust and corrosion resisting material such as bronze, stainless steel, copper or the like, each fitting having four laterally extending bosses35. These bosses have two pair of axially aligned openings at right angles to one another. The inlet openings 35 and 31 of the fitting 3| are preferably tapped to receive the threaded end of the stub shaft i4 and oneend of the central shaft [3, while the transverse openings 38 and 39 are made to closely receive the ends of the tubing 32 or 34 for a sweated or brazed fit.

A diagonally disposed partition 4! within eachfitting divides the fitting into two' chambers whereby each inletopening is connected with a transversely extending discharge opening.

The circulation of the heating or cooling fluid through the coils is indicated by the arrows in Figure 2. It passes through the stub shaft l4 into the fitting 3| where it is diverted by the partition 4| into the heat transfer coil 32. After passing through this coil to the opposite end of the vat, it passes into the second fitting 33 where it is diverted back through the central shaft 13 to the first fitting 3!. Here the baffle 4| again diverts it, but through the second coil 34. After passing through the second coil it again reaches the rear end of the vat and is discharged by the second fitting through the stub shaft i6.

In the modified form of diversion fitting illustrated at 42 in Figure 3, the only difference is that the partition 43 is straight rather than diagonal, and the openings 44 and 46 for receiving the tubing are not in axial aligmnent.

Although I have described several specific embodiments of my invention, it is apparent that modifications thereof may be made by those skilled in the art. Such modifications may be made without departing departing from the spirit and scope of my invention as set forth in the appended claims.

I claim as my invention:

1. In a device of the character described, a pair of heater members having relatively large heat transfer surfaces wound in helical, substantially parallel fashion, a tubular central shaft, means for directing a heat transfer medium through one of said heater members, means for redirecting the heat transfer medium back through the central shaft, and means for again redirecting the heat transfer "medium to pass it through the other of the said heater members.

2. In a device of the character described, a pair of heater coils wound in'helical, substantially parallel fashion, a tubular shaft disposed axially thereof, means for feeding a heat transfer fluid throughthe input end of the tubular shaft into one of the heater coils, means for exhausting said fiuid into the tubular shaft, means for discharging the fiuid from the tubular shaft into the second of the heater coils at a point adjacent the input end of the'first heater coil, and means for discharging the fluid from the second heater coil through the end of the tubular shaft opposite the input end.

3. In a device of the character described, a pair of heat transfer members wound in helical substantially parallel fashion, a tubular shaft disposed axially of the heat transfer 'members, means forming a connection between the ends of each heat transfer member adjacent the inlet and discharge ends of the tubular shaft, and partition means disposed within the tubular shaft adjacent the junctions of the heat transfer members and the tubular shaft whereby a continuous channel for conducting a fiuid is provided from the input end of the tubular shaft to a point adjacent the outlet end of the shaft, back through.

the tubular'shaft to a point adjacent the input end of theshaft, and back again to and through the discharge-end of the tubular shaft.

4. In a device of the character described, a'pair of tubular heater coils wound in substantially parallel relation and in helical fashion, with the turns ofeach c'oilhaving a double pitch lead, a substantially tubular shaft disposed axially of the coils, theends of said coils being connected to the tubular shaft adjacent the ends, and partition means within the shaft and adjacent th points of connection of the shaft and the ends of the coils whereby the tubular shaft is divided into three chambers with the'first of saidchambers connected with the inlet of the first of said heater coils, with the second of the-saidchambers connected with'the outlet of the first and the inlet of the second of said heater coils, and with the outlet of the second heater coil connected with the third of said chambers.

NEWEL F; HODGDON. 

